#include "kernel.h"
#include "string.h"
#include "stdarg.h"

#define is_digit(c) ((c) >= '0' && (c) <= '9')

static int skip_atoi(const char** s)
{
    int i = 0;
    while (is_digit(**s))
    {
        i = i * 10 + (*((*s)++) - '0');
    }
    return i;
}

#define ZEROPAD 1
#define SIGN 2
#define PLUS 4
#define SPACE 8
#define LEFT 16
#define SPECIAL 32
#define SMALL 64

#define do_div(n, base) ({\
    int __res; \
    __asm__("div %4" : "=a"(n), "=d"(__res): "0"(n), "1"(0), "r"(base)); \
    __res;})

static char* number(char* str, int num, int base, int size, int precision, int type)
{
    char c, sign, tmp[36];
    const char* digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    int i;

    if (type & SMALL)
    {
        digits = "0123456789abcdefghijklmnopqrstuvwxyz";
    }

    if (type & LEFT)
    {
        type &= ~ZEROPAD;
    }

    if (base < 2 || base > 36)
    {
        return NULL;
    }

    c = (type & ZEROPAD) ? '0' : ' ';
    if ((type & SIGN) && num < 0)
    {
        sign = '-';
        num = -num;
    } else {
        sign = (type & PLUS) ? '+' : ((type & SPACE) ? ' ' : 0);
    }
    if (sign)
    {
        size--;
    }
    if (type & SPECIAL)
    {
        // 要添0x，所以要减2
        if (base == 16)
        {
            size -= 2;
            // 要添0，所以要减1
        } else if (base == 8)
        {
            size--;
        }
    }
    
    i = 0;
    if (num == 0)
    {
        tmp[i++] = '0';
    } 
    else 
    {
        while (num != 0)
        {
            tmp[i++] = digits[do_div(num, base)];
        }
    }
    if (i > precision)
    {
        precision = i;
    }
    size -= precision;
    if (!(type & (ZEROPAD + LEFT)))
    {
        while (size-- > 0)
        {
            *str++ = ' ';
        }
    }
    if (sign)
    {
        *str++ = sign;
    }

    if (type & SPECIAL)
    {
        if (base == 8)
        {
            *str++ = '0';
        } 
        else if (base == 16)
        {
            *str++ = '0';
            *str++ = digits[33];
        }
    }
    if (!(type & LEFT))
    {
        while (size-- > 0)
        {
            *str++ = c;
        }
    }
    while (i < precision--)
    {
        *str++ = '0';
    }
    while (i-- >0)
    {
        *str++ = tmp[i];
    }
    while (size-- > 0)
    {
        *str++ = ' ';
    }
    return str;
}

int vsprintf(char* buf, const char* fmt, va_list args)
{
    int len;
    int i;
    char* str;
    char* s;
    int *ip;

    int flags;
    int field_width;
    int precision;
    int qualifier;

    for (str = buf; *fmt; ++fmt)
    {
        if (*fmt != '%')
        {
            *str++ = *fmt;
            continue;
        }
        
        flags = 0;
        repeat:
            ++fmt;
            switch (*fmt)
            {
            case '-':
                flags |= LEFT; goto repeat;
            case '+':
                flags |= PLUS; goto repeat;
            case ' ':
                flags |= SPACE; goto repeat;
            case '#':
                flags |= SPECIAL; goto repeat;
            case '0':
                flags |= ZEROPAD; goto repeat;
            }
            field_width = -1;
            if (is_digit(*fmt))
            {
                field_width = skip_atoi(&fmt);
            }
            else if (*fmt == '*')
            {
                field_width = va_arg(args, int);
                if (field_width < 0)
                {
                    field_width = -field_width;
                    flags |= LEFT;
                }
            }

            precision = -1;
            if (*fmt == '.')
            {
                ++fmt;
                if (is_digit(*fmt))
                {
                    precision = skip_atoi(&fmt);
                }
                else if (*fmt == '*')
                {
                    precision = va_arg(args, int);
                }
                if (precision < 0)
                {
                    precision = 0;
                }
            }

            qualifier = -1;
            if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L')
            {
                qualifier = *fmt;
                ++fmt;
            }
            switch (*fmt)
            {
            case 'c':
                if (!(flags & LEFT))
                {
                    while (--field_width > 0)
                    {
                        *str++ = ' ';
                    }
                }
                *str++ = (unsigned char)va_arg(args, int);
                while (--field_width > 0)
                {
                    *str++ = ' ';
                }                
                break;
            case 's':
                s = va_arg(args, char*);
                len = strlen(s);
                if (precision < 0)
                {
                    precision = len;
                }
                else if (len > precision)
                {
                    len = precision;
                }
                if (!(flags & LEFT))
                {
                    while (len < field_width--)
                    {
                        *str++ = ' ';
                    }
                }
                for (i = 0; i < len; i++)
                {
                    *str++ = *s++;
                }
                while (len < field_width--)
                {
                    *str++ = ' ';
                }
                break;
            case 'o':
                str = number(str, va_arg(args, unsigned long), 8, field_width, precision, flags);
                break;
            case 'p':
                if (field_width == -1)
                {
                    field_width = 8;
                    flags |= ZEROPAD;
                }
                str = number(str, (unsigned long)va_arg(args, void*), 16, field_width, precision, flags);
                break;
            case 'x':
                flags |= SMALL;
            case 'X':
                str = number(str, va_arg(args, unsigned long), 16, field_width, precision, flags);
                break;
            case 'd':
            case 'i':
                flags |= SIGN;
            case 'u':
                str = number(str, va_arg(args, unsigned long), 10, field_width, precision, flags);
                break;
            case 'n':
                ip = va_arg(args, int*);
                *ip = (str - buf);
                break;
            case '%':
                *str++ = '%';
                break;
            default:
                if (*fmt)
                    *str++ = *fmt;
                else
                    --fmt;
                break;
            }
    }
    *str = '\0';
    return (int)(str - buf);
}